Cognitive Development

Students
of cognitive development ask how our young are able to acquire and
use knowledge about the physical, social, cultural, and mental worlds.
Questions of special interest include: what is known when; whether
what is known facilitates or serves as a barrier to the accurate
interpretation and learning of new knowledge; how knowledge development
serves and interacts with problem-solving strategies; and the relationship
between initial knowledge levels and ones achieved for everyday
as opposed to expert use.

Several classes of theories share
the premise that infants lack abstract representational abilities
and therefore CONCEPTS. The infant mind to
an associationist is a passive "blank slate" -- upon
which a wash of sensations emanating from the world is recorded
as a result of the associative capacity. Stage theorists need not
share the no innate knowledge assumption. Interestingly, however, PIAGET, Bruner,
and VYGOTSKY do, although to them infants are
able to participate actively in the construction of their own cognitive
development. For Piaget, neonates spontaneously practice their reflexes,
the effect being the differentiation of inborn reflexes into different
sensory-motor schemes. Active use of these yields integrated action schemes,
and thus novel ways to act on the environment (Piaget 1970). The information
processing approach emphasizes the development of general processes
like ATTENTION, short- and long-term memory,
organization, and problem solving. The focus is on how learning
and/or maturation overcome limits on information processing
demands (Anderson 1995) and the development of successful PROBLEM SOLVING (Siegler
1997). Much attention is paid to how knowledge systems are acquired
and circumvent these real-time limits on various processes. When
it comes to the matter of what the newborn knows, the answer almost always
is "nothing" (but see Mandler 1997). Thus, many cognitive
development models are firmly grounded on associationist assumptions.

Reports of early conceptual competencies
have encouraged the development of models that grant infants some knowledge
to begin with. These include symbolic connectionist accounts that
share much with associationist theories and modern instantiations
of rationalism. In the latter case, humans are endowed with some
innate ideas, modules, and/or domain-specific structures
of mind. Possible candidates for innate endowments include implicit
concepts about natural number, objects, and kinds of energy sources
of animate and inanimate objects (Gelman and Williams 1997; Keil
1995; Pinker 1994). These kinds of models are learning models, ones
built on the assumption that there is more than one learning mechanism.
The idea is that there is a small set of domain-specific, computational
learning devices -- each with a unique structure and information
processing system -- that support and facilitate learning
about the concepts of their domains. Gelman and Williams (1998)
refer to these as skeletal-like, ready to assimilate and accommodate domain-relevant
inputs, but very sketchy at first. Knowledge is not sitting in the
head, ready to spring forth the moment the environment offers one
bit of relevant data. But structures, no matter how nascent, function
to support movement along a domain-relevant learning path by encouraging
attention to and fostering storage of domain-relevant data.

For most associationist, stage, and
information processing theorists, it takes a long time for newcomers
to the world to develop concepts, because infants must first build
up large memories of bits of sensory and response experiences; associate,
connect, or integrate these in ways that represent things or events;
associate, connect, or integrate the latter, and so on. The young
mind's progress toward conceptual understandings is slow,
from reliance on the sensory, on to use of perceptions, and eventually
to developing the wherewithal to form abstract concepts and engage
in intelligent problem solving. This common commitment to the traditional
view that concepts develop from the concrete or perceptual to the abstract
plays out differently depending on whether one is a stage theorist
or not. For a non - stage theorist, the march to the abstract
level of knowing is linear and cumulative. For a stage theorist,
the progress usually involves movement through qualitatively different
mental structures that can assimilate and use inputs in new ways.
Many of the results of classification tasks used by Bruner, Piaget,
and Vygotsky encourage the concrete-to-abstract characterization
of cognitive development. Repeatedly, it is found that two- to six-year-olds
do not use classification criteria in a consistent fashion. For
example, when asked to put together objects that go together, one
preschool child might make a train, another a long line of alternating
colors, while another might focus on appearance as opposed to reality,
and so on.

It is important to recognize that
all theories of cognitive development grant infants some innate
abilities. The abilities to receive punctate sensations of light,
sound, or pressure, and so on, and form associations according to
the laws of association (frequency and proximity) are foundational
for associationists. Association between sensations and responses
is the groundwork for knowledge of the world at a sensory and motor
level. These in turn support knowledge acquisition at the perceptual
level. Experiences at the perceptual level provide the opportunity
for cross-modal associative learning and the eventual induction
of abstract concepts that are not grounded on particular perceptual information.
Although there are important differences in the foundational assumptions
of the association and traditional stage accounts, their characterizations
of an infant's initial world are more similar than not.
For example, associations are not Piaget's fundamental
units of cognition; sensori-motor schemes are. But to him, an infant's
initial knowledge is limited to innate reflexes and is combined
with an inclination to actively use and adapt these as a result
of repeated interactions with objects. This eventually leads to the
development of intercoordinated schemes and movement to action-based
representations that take the infant from an out-of-sight, out-of-mind
stage to internalized representations, the mental building blocks
of a world of three-dimensional objects in a three-dimensional space.

Piaget's basic assumptions
about the nature of the data that feed early development apply to
other stage theorists. In general, what initially count as relevant
inputs are simple motoric, sensory, or perceptual features. His
emphasis is more on children's active participation in
their own cognitive development. Bruner and Vygotsky concentrate
more on how others help the young child develop coherent knowledge
about their social, cultural, and historical environments. Still,
all concur that initial "concepts" are sensori-motor
or perceptual in form and content; these are variously labeled as
graphic collections, preconcepts, complexes, pseudoconcepts, and
chain concepts. Thus, whether the account of the origins of knowledge
is rooted in an associationist, information processing, or stage
theory, the assumption is that first-order sense data, for example sensations
of colored light, sound, pressure, etc., serve as the foundation
upon which knowledge is developed. Principles or structures that
organize the representations of concepts are a considerably advanced
accomplishment, taking hold somewhere between five and seven years
of age.

Those who embrace more rationalist
accounts assume that the mind starts out with much more than the
ability to sense and form associations or schemas about sensations
and reflexes. Beginning learners have some skeletal structures with
which to actively engage the environment; domain-relevant inputs are
those that can be brought together and mapped to the existing mental
structure. Put differently, skeletal mental structures are attuned
to information in the environment at the level of structural universals,
not the level of surface characteristics. Thus the nature of relevant
data, even for beginning learners, can be rather abstract. It need
not be bits of sensation or concrete. Young learners can have abstract concepts.

We now know that preschool-age children
appeal to invisible entities to explain contamination, invoke internal
or invisible causal forces to explain why objects move and stop,
reason about the contrast between the insides and outsides of unfamiliar animals,
choose strategies that are remarkably well suited to arithmetic
problems, pretend that the same empty cup is first a full cup and
then an empty cup, etc. Five-month-old infants respond in ways consistent
with the beliefs that one solid object cannot pass through another
solid object; an inanimate object cannot propel itself; and that
mechanical and biomechanical motion are very different (see Wellman and
S. Gelman 1997 for details and more examples).

With development, core knowledge
systems can become extremely rich, whether or not formal schooling
is available -- so much so that the existing knowledge structure
behaves like a barrier for learning new structures in the domain
(Gelman 1993). For example, the intuitive belief that an inanimate
object continues to move in a circle because it currently has such
a trajectory is inconsistent with the theory of Newtonian mechanics.
Yet the belief is held by many college students who have had physics
courses. Similarly, our well-developed NAIVE MATHEMATICS,
sometimes called "street mathematics" (Nunes, Schliemann,
and Carraher 1993), makes it hard to learn school mathematics. In
these cases, school lessons do not suffice to foster new understandings
and kinds of expertise. Be they nativist or nonnativist in spirit,
efforts to account for the course of cognitive development will
have to incorporate this fact about the effect, or lack of effect,
of experience on learning and concept acquisition